<template>
  <div>
    <h1>当前求和为：{{sum}}</h1>
    <select v-model.number="number">
      <option value="1">1</option>
      <option value="2">2</option>
      <option value="3">3</option>
    </select>

    <button @click="increment">+</button>
    <button @click="decrement">-</button>
    <button @click="incrementOdd">当前求和为奇数再加</button>
    <button @click="incrementWait">等一等再加</button>
  </div>
</template>

<script>
  export default {
    name: 'Count',
    data() {
      return {
        number: 1,  // 用户选择的数字
        sum: 0  // 当前的和
      }
    },
    methods: {
      increment() {
        this.sum += this.number
      },
      decrement() {
        this.sum -= this.number
      },
      incrementOdd() {
        if (this.sum % 2) {
          this.sum += this.number
        }
      },
      incrementWait() {
        setTimeout(() => {
          this.sum += this.number
        }, 500)
      }
    }
  }
</script>

<style>
button {
  margin-left: 5px;
}
</style>